Chlorine dioxide has become increasingly well known as a potent antimicrobial agent, as well as a bleaching material, in many commercial and industrial applications. As a germicide it is finding increasing use in municipal water disinfection, cooling towers and oral malodorants, where it both destroys putrefactive organisms and oxidizes the odorant. It also has been approved recently for reducing poultry pathogens during processing, surpassing the reductions which can be achieved with chlorine. Chlorine dioxide is also used as a bleaching agent in paperboard production and for textiles and flour. However, ClO.sub.2 is a reactive gas which is explosive in air at levels approximating 10%, and it has a low threshold limit value (TLV) classification by OSHA of 0.1 ppm in workers' air. It cannot be compressed and stored, as can chlorine, and water solutions of chlorine dioxide rapidly degrade both through disproportionation to higher- and lower-valent chlorine species and through evaporation. As a result of these limiting properties, it is generally produced "on site," by acidification of chlorite solutions or reduction of chlorates.
Because it has superior destructive properties for bacteria, fungi and viruses, efforts have been made to capture and/or stabilize ClO.sub.2 molecules in aqueous solution for subsequent use as a germicide or for more general oxidative purposes. A series of patents have issued in the last forty years, disclosing the stabilization of ClO.sub.2 solutions by inclusion of various peroxides, such as sodium perborate in U.S. Pat. No. 2,701,781, and sodium carbonate peroxide in U.S. Pat. No. 3,123,521. Chlorine dioxide may form in these solutions after dilution with water, which may reduce the pH sufficiently to produce low levels of the gas at a slow rate, or by direct acidification of the solutions to hasten the process. The stabilized chlorine dioxide in these formulations has been later revealed to predominate in the reduced oxychlorine form of chlorite, with chlorine in the trivalent state, rather than as chlorine in the tetravalent state associated with ClO.sub.2. The interaction of acidity with chlorites is a well recognized means of converting chlorite to chlorine dioxide. The essence of these stabilized ClO.sub.2 patents is the presence of a peroxide reservoir, which acts to reduce any small levels of free ClO.sub.2, that may be slowly formed, back to the more stable chlorite form. Analysis of commercially available stabilized chlorine dioxide formulations reveal, at most, only a few parts per million of free, molecular ClO.sub.2.
A novel polymer composition was disclosed, in U.S. Pat. No. 4,829,129, where aqueous polymeric N-vinyl-.alpha.-pyrrolidone (PVP) solutions, ranging from 1% to 60% by weight, are saturated with ClO.sub.2 gas. The gas reacts with the PVP causing the characteristic chlorine dioxide color to disappear. Certain other polymer types are disclosed which possess similar properties. The resulting product is an organically stabilized chlorine dioxide composition which is claimed to be a powerful microbicide, although no examples are provided to confirm this claim. The stabilized ClO.sub.2 is postulated to exist in the reduced, trivalent chlorine, chlorite form, which is stabilized or complexed by the PVP. A related, chemically stabilized chlorite matrix is revealed by Kuhne in U.S. Pat. Nos. 4,507,285 and 4,725,437, which matrices enclose activated oxygen for topical or systemic treatment of diseases and disorders.
In all of these teachings and disclosures there is no indication that free molecular ClO.sub.2 can be held in solution per se, in the tetravalent chlorine form, for subsequent release by means other than acidification of the reduced chlorite form and partial chemical conversion to chlorine dioxide, i.e. from [H.sup.+ ]+[ClO.sub.2.sup.- ].fwdarw..fwdarw..fwdarw.ClO.sub.2, [Cl.sup.- ], [ClO.sub.3.sup.- ]. In many instances, however, the use of acids is counterindicated for certain applications. Specifically, a continued search has revealed that if significant levels of ClO.sub.2 are required for, say, localized disinfection, wound treatment, or mouth odor oxidation, without the use of acid triggers of chlorite solutions, including so-called stabilized or complexed ClO.sub.2 solutions, no compositions have yet been described which can meet this need. This invention was made as a result of that search.